A Transmission Electron Microscope, hereinafter TEM, and a Scanning Transmission Electron Microscope, hereinafter STEM, have enhanced high spatial resolution at an atomic level, so that a crystal lattice image can be observed. A crystal lattice has a periodic structure inside thereof, and there are several useful measuring methods using this periodicity.
Especially, the STEM can observe atomic columns directly by a high angle annular dark field, hereinafter HAADF. The STEM has a merit of being able to observe multiple signals including this HAADF signal all at once. However, STEM images take longer time to acquire a single image than TEM images because it uses a scanning method. For instance, it takes 1 minute or more for obtaining enough signal intensity to observe a crystal lattice image of 50 nm square area in a typical STEM measurement. A commercially-supplied STEM has positional instability of about 1 nm per minute. Atomic distances of most materials are less than 1 nm. If the required accuracy is less than one atomic lattice distance with the image whole, the accuracy cannot be fulfilled.
Further, it is incompatible in present conditions to keep a high spatial resolution able to observe the crystal lattice image, and to obtain an image of a large area. Under the condition of high spatial resolution for scan steps, a scanning time is proportional to the scanning area. For instance, if the scale (magnification) of the scanning region is changed by 10 times, the scanning area and time become huge with changing by 100 times, because an area is proportional to the 2nd power. Thus, a high spatial resolution in a large area takes time, which causes a large shift of the image, and high accuracy observation becomes difficult.